1. Field of the Invention
This invention relates to polymerization of vinylpyrrolidone to form polyvinylpyrrolidone polymers, and more particularly, to a precipitation polymerization process for preparing homopolymers of polyvinylpyrrolidone in high yield in the form of fine powders at a high polymer solids level.
2. Description of the Prior Art
Polyvinylpyrrolidone (PVP) can be made by solution, suspension or emulsion polymerization of vinylpyrrolidone monomer in the presence of water or organic solvents. Lorenz and Williams U.S. Pat. No. 4,190,718, for example, disclosed a process for making high molecular weight PVP in heptane by reverse suspension polymerization using suitable suspending agents. Belgium patent 668,368 also described a process for synthesizing copolymers of vinyl lactams in aliphatic hydrocarbon solvents by precipitation polymerization. However, these and other references have failed to provide a commercial process for making homopolymers of polyvinylpyrrolidone in high yield in the form of fine powders at a high polymer solids level.
Accordingly, it is the object of this invention to provide a new and improved process for making homopolymers of polyvinylpyrrolidone in high yield in the form of fine powders at a high polymer solids level.
A particular object herein is to provide homopolymers of polyvinylpyrrolidone in a yield of at least about 95%, as fine powders, preferably at a polymer solids level of at least about 17%, and, most preferably 30% or more.
These and other objects and features of the invention will be made apparent from the following description of the invention.